Piezoelectric/electrostrictive film type elements and process for producing the same

ABSTRACT

An integrated piezoelectric/electrostrictive film type element with excellent durability, includes a substrate made of a ceramic material composed mainly of completely stabilized of partially stabilized zirconium oxide, and a piezoelectric/electrostrictive operating section integrated onto the ceramic substrate by a film-forming method, the piezoelectric/electrostrictive operating section comprising a lower electrode, a piezoelectric/electrostrictive layer of a lead element-containing composition, and an upper electrode, wherein a heterophase-occurrence rate at a surface of the piezoelectric/electrostrictive layer is controlled to a range of 0.1 to 30%.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] The present invention relates to piezoelectric/electrostrictivefilm type elements of a unimorph type or a bimorph to be used as varioustransducers, various actuators, etc. In particularly, the invention isaimed at advantageously improving durability of suchpiezoelectric/electrostrictive film type elements without deterioratingtheir piezoelectric/electrostrictive performance.

[0003] The piezoelectric/electrostrictive film type elements accordingto the present invention arc intended to include elements for convertingelectric energies to mechanical energies, i.e., mechanicaldisplacements, stress or vibration as well as elements for effectingreverse conversions thereof. Since the elements according, to he presentinvention have dielectric property as well as thepiezoelectric/electrostrictive performance, they can be also used asfilmy condenser elements, etc.

[0004] (2) Related Art Statement

[0005] The piezoelectric/electrostrictive elements are used in widefields including various transducers for converting electric energies tomechanical energies, i.e., mechanical displacements, forces orvibration, as well as elements for effecting reverse conversionsthereof, various actuators, functional parts operating at apredetermined frequency range such as filters, various display devicessuch as displays, sound-emitting members such loudspeakers, sensors suchas microphones and ultrasonic wave sensors, etc.

[0006] For example, there is known a piezoelectric/electrostrictiveelement as shown in FIG. 1(a) which comprises a ceramic substrate 1functioning as a vibrating plate, and a film-typepiezoelectric/electrostrictive operating section 5, provided on thesubstrate 1, that is constituted by a first electrode film 2 as a lowerelectrode, a piezoelectric/electrostrictive layer 3 and a secondelectrode film 4 as an upper electrode (JP-A-3-128,681) In addition,there is also known a piezoelectric/electrostrictive element as shown inFIG. 1(b) in which a ceramic substrate 1 is provided with a cavity, anda bottom portion of the cavity is used as a vibrating section 1 a, and apiezoelectric/electrostrictive operating section 5 is integrally formedon the outer surface of the vibrating section 1 a (JP-A-5-49,270).

[0007] As ceramic substrates constituting suchpiezoelectric/electrostrictive elements, ceramic materials composedmainly of zirconium oxide partially stabilized with yttrium oxide aregenerally known (for example, JP-A 5-29,675, JP-A-5-97,437 andJP-A-5-270,912).

[0008] Use environments have recently variously changed withdiversification in the piezoelectric/electrostrictive devices.Particularly, when the use environment in which the above-mentionedpiezoelectric/electrostrictive film type elements are used is of ahigher temperature and more humid atmosphere compared with conventionalconditions, deterioration in material of the substrate poses a problem.

[0009] That is, if the piezoelectric/electrostrictive film element isused in the above higher temperature and more humid environment, thereis a tendency that the substrate begins to be degraded in thepiezoelectric/electrostrictive film type, element than thepiezoelectric/electrostrictive operating section.

SUMMARY OF THE INVENTION

[0010] The present invention has been developed in view of the aboveactual circumstances, and is aimed at the provision of integratedpiezoelectric/electrostrictive film type elements having excellentdurability and an advantageous producing process thereof, withoutcausing degradation in material of the substrate or lowering thepiezoelectric/electrostrictive performance or deteriorating thecharacteristics of the piezoelectric/electrostrictive layer, even ifused under the high-temperature and highly humid atmosphere

[0011] In the following, the elucidation process of the presentinvention will be explained.

[0012] After having repeatedly performed strenuous investigations toaccomplish the above object, the present inventors discovered that thesubstrate was deteriorated by lead element entering the substrate duringthe production. That is, although a ceramic material composed mainly ofzirconium oxide has been formerly used as the substrate, it wasclarified that the lead element entering such a ceramic substraterapidly damaged the durability of the substrate when used in thehigh-temperature and highly humid condition.

[0013] Therefore, the present inventor then examined causes why the leadelement entered into the substrate, and discovered that such a leadelement entered the substrate when firing (thermally treating) thepiezoelectric/electrostrictive material. That is, a lead-containingmaterials having excellent properties (such as lead zirconate titanate,etc.) was generally used as the piezoelectric/electrostrictive material,and a film of such a material was ordinarily formed as apiezoelectric/electrostrictive layer, and integrated by firing.

[0014] When a piezoelectric/electrostrictive layer made of such alead-containing material is to be formed (by firing), the atmosphere isformerly controlled under condition with a high lead concentration toprevent the evaporation of the lead element contained in thepiezoelectric/electrostrictive material during firing, since suchevaporation may cause changes in the composition of thepiezoelectric/electrostrictive layer to thereby deteriorate thepiezoelectric/electrostrictive performance.

[0015] As mentioned above, the piezoelectric/electrostrictive layer isformerly fired with a lead concentration-increased atmosphere in thepresence of an evaporating source of a lead-containing material or thelike so as to prevent the deterioration in the above characteristics.However, when the piezoelectric/electrostrictive layer is fired in theatmosphere with such a high lead concentration, the lead element in theatmosphere penetrates into the ceramic substrate composed mainly ofzirconium oxide, which causes deterioration in the quality of thesubstrate as mentioned before.

[0016] In order to solve the above problems, the present inventorsrepeatedly performed numerous experiments and examinations, and acquiredthe following knowledge.

[0017] (1) The firing atmosphere needs not always be an atmospherehaving a high concentration of lead, even if thepiezoelectric/electrostrictive layer contains the lead element. If somelead element evaporates from the piezoelectric/electrostrictive layerduring firing, no deterioration occurs in thepiezoelectric/electrostrictive layer.

[0018] (2) The rate of a heterophase occurring at a surface of thepiezoelectric/electrostrictive layer during firing is preferable as anindex for the judgment of the evaporated amount of the lead element fromthe piezoelectric/electrostrictive layer.

[0019] (3) The integrated piezoelectric/electrostrictive film typeelement in which the area rate of the heterophase occurring duringfiring is controlled to a range of 0.1 to 30% by adjusting the firingconditions suffers from neither degradation in quality in the substrateand deterioration in the characteristics of thepiezoelectric/electrostrictive layer even when in use underhigh-temperature and highly humid atmosphere.

[0020] The present invention is based on the above recognition.

[0021] That is, the substantial features of the present invention are asfollows.

[0022] (1) An integrated piezoelectric/electrostrictive film typeelement having excellent durability and comprising a substrate made of aceramic material composed mainly of completely stabilized or partiallystabilized zirconium oxide, and a piezoelectric/electrostrictiveoperating section integrated onto the ceramic substrate by afilm-forming method, said piezoelectric/electrostrictive operatingsection comprising a lower electrode., a piezoelectric/electrostrictivelayer of a lead element-containing composition, and an upper electrode,wherein a heterophase-occurrence rate at a surface of thepiezoelectric/electrostrictive layer is controlled to a range of 0.1 to30%.

[0023] (2) The integrated piezoelectric/electrostrictive film typeelement of above (1) having excellent durability in which the ceramicsubstrate is shaped in the form of a thin diaphragm portion, and saidpiezoelectric/electrostrictive operating section is integrally formed onan outer surface of the diaphragm portion.

[0024] (3) The integrated piezoelectric/electrostrictive film typeelement of above (1) or (2) having excellent durability in which theheterophase-occurrence rate is controlled to a range of 1 to 10%.

[0025] (4) The integrated piezoelectric/electrostrictive film typeelement of above (1) or (2) having excellent durability in which theaverage grain size of crystals constituting the ceramic substrate is 0.1to 2.0 μm.

[0026] (5) The integrated piezoelectric/electrostrictive film typeelement of above (1) or (2) having excellent durability in which athickness of the piezoelectric/electrostrictive layer is not more than100 μm

[0027] (6) The integrated piezoelectric/electrostrictive film typeelement above (1) or (2) having excellent durability in which athickness of the piezoelectric/electrostrictive operating section is notmore than 150 μm.

[0028] (7) The integrated piezoelectric/electrostrictive film typeelement of above (2) in which a thickness of the diaphragm portion isnot more than 50 μm.

[0029] (8) A process for producing an integratedpiezoelectric/electrostrictive film type element having excellentdurability, comprising the steps of preparing a substrate made of aceramic material composed mainly of completely stabilized or partiallystabilized zirconium oxide, and successively forming a lower electrode,a piezoelectric/electrostrictive layer of a lead element-containingcomposition, and an upper electrode on the ceramic substrate by afilm-forming method, said lower electrode, saidpiezoelectric/electrostrictive layer and the upper electrodeconsitituting a piezoelectric/electrostrictive operating section and atleast said piezoelectric/electrostrictive layer being fired, wherein aproduced rate of a heterophase occurring at a surface of thepiezoelectric/electrostrictive layer is controlled to a range of 0.1 to30% in terms of an area rate by adjusting a concentration of lead in afiring atmosphere and/or an amount and a speed of a running fluid of thefiring atmosphere.

[0030] (9) The highly durable, integrated piezoelectric/electrostrictivefilm type element-producing process of above (8) in which the atmosphereis controlled by adjusting at least one condition selected from thefollowing four conditions: i) a composition ratio, a configuration, aweight ad an arranged location of an evaporating source containing leadas a constituent element; iii) an arranged location of apiezoelectric/electrostrictive material in a firing furnace or a firingvessel; iii) an opening degree of the firing furnace or the firingvessel; and v) feeding an absorbent for absorbing a lead element in thefiring atmosphere.

[0031] These and other objects, features and advantages of the inventionwill be appreciated upon reading the following description of theinvention when taken in conjunction with the attached drawings, with theunderstanding that some modifications, variations and changes could bemade by the skilled person in the art to winch the invention pertains.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] For a better understanding of the invention, reference is made tothe attached drawings, wherein:

[0033]FIG. 1(a) is a partially cut-away, perspective view of a planarpiezoelectric/electrostrictive film type element, and FIG. 1(b) is apartially cut-away, perspective view of a piezoelectric/electrostrictivefilm type element having a cavity structure, the present invention beingapplicable to both of the elements;

[0034] FIGS. 2(a) and 2(b) are sectional views of thepiezoelectric/electrostrictive film type elements in FIGS. 1(a) and 1(b)along A-A and B-B, respectively;

[0035]FIG. 3 is a graph showing the relationships between theheterophase-occurrence rate and the piezoelectric/electrostrictiveperformance or the durability;

[0036]FIG. 4 is a perspective view of a further embodiment of thepiezoelectric/electrostrictive film type element according to thepresent invention;

[0037]FIG. 5 is a perspective view of a still further embodiment of thepiezoelectric/electrostrictive film type element according to thepresent invention;

[0038]FIG. 6 is a perspective view of a still further embodiment of thepiezoelectric/electrostrictive film type element according to thepresent invention;

[0039]FIG. 7 is a perspective view of a still further embodiment of thepiezoelectric/electrostrictive film type element according to thepresent invention;

[0040]FIG. 8 is a perspective view of a still further embodiment of thepiezoelectric/electrostrictive film type element according to thepresent invention;

[0041] FIGS. 9(a) and 9(b) are perspective views from rear and frontsurface sides of a modified embodiments of thepiezoelectric/electrostrictive film type element shown in FIG. 8,respectively;

[0042]FIG. 10(a) and 10(b) are views showing a connecting configurationto an electrode film according to the present invention;

[0043]FIG. 11 is a view showing another connecting configuration to anelectrode film according to the present invention;

[0044]FIG. 12 is a view showing a further connecting configuration to anelectrode film according to the present invention;

[0045] FIGS. 13(a) and 13(b) are views showing apiezoelectric/electrostrictive film type actuator to which the presentinvention is applied;

[0046] FIGS. 14(a) and 14(b) are views showing an acceleration sensorelement to which the present invention is applied;

[0047]FIG. 15 is a piezoelectric/electrostrictive film type displacementelement to which the present invention is applied; and

[0048]FIG. 16 is a reflection electron image photograph of a surface ofa piezoelectric/electrostrictive layer with a scanning electronmicroscope.

DETAILED DESCRIPTION OF THE INVENTION

[0049] In the following, the present invention will be explained in moredetail with reference to the attached drawings.

[0050] FIGS. 1(a) and 1(b) are perspective views ofpiezoelectric/electrostrictive film type elements (actuators) accordingto the present invention, and FIGS. 2(a) and 2(b) sectional viewsthereof along A-A and B-B, respectively.

[0051] In these figures, the piezoelectric/electrostrictive film typeelement in FIGS. 1(a) and 2(a) is of a general structure in which apiezoelectric/electrostrictive operating section composed of a lowerelectrode, a piezoelectric/electrostrictive layer and an upper electrodeis formed on a planar ceramic substrate. On the other hand, thepiezoelectric/electrostrictive element, in FIGS. 1(a) and 2(b) is of aso-called cavity structure in which outer edge portions of a substrateare thick. This structure element has an advantage that an inner portion(diaphragm portion:substantially vibrating section) sandwiched betweenthe thick outer edge portions can be made particularly thin.

[0052] In FIGS. 1 and 2, reference numeral 1 denotes a ceramicsubstrate, 2 a first electrode film (lower electrode), 3 a filmypiezoelectric/electrostrictive layer, and 4 a second electrode film(upper electrode). They are successively laminated upon the ceramicsubstrate 1 (through firing) by a film-forming method, therebyconstituting a piezoelectric/electrostrictive operating section 5 as anintegrated multi-layered structure. In case of the cavity structure, 1 aand 1 b denote the vibrating section and the thick outer edge portion,respectively, and 6 a cavity.

[0053] The first and second electrode film 2 and 4 extend outwardly froman edge portion of the piezoelectric/electrostrictive layer 3 to formlead portions 2 a and 4 a, respectively. Voltage is applied to theelectrode films 2 and 4 through the lead portions 2 a and 4 arespectively.

[0054] Further, the ceramic substrate 1 finally takes a sintered state.The ceramic substrate may be formed by preliminarily sintering prior tothe formation (firing) of the piezoelectric/electrostrictive operatingportion 5 of the piezoelectric/electrostrictive film type elementaccording to the above embodiments. Alternatively, the substrate may beformed by preparing a green sheet of a substrate-forming material,forming a piezoelectric/electrostrictive section 5 on the green sheet bya film-forming method mentioned later and simultaneously sintering them.The substrate may be also formed by forming a first electrode film 2 anda piezoelectric/electrostrictive layer 3 on such a green sheet and thensintering them.

[0055] Among the above, the method by which the ceramic substrate 1 isformed by preliminary sintering is advantageous sly employed in thatwarping of the element can be reduced and that a necessary precision inthe pattern dimension can be realized. Further, according to thismethod, the temperature in firing for the integral lamination of thepiezoelectric/electrostrictive layer 3 onto the ceramic substrate can beset at less than a sintering temperature of the ceramic substrate 1.

[0056] As shown in FIG. 1(b), in case of the ceramic substrate having acavity structure, a green sheet for a vibrating plate and a green sheetprovided with a hollow space corresponding to such a cavity by using amold or machining such as ultrasonic machining are laminated one uponanother as first and second layers, subjected to a thermal compressionbonding to each other and fired. FIG. 1(b) takes the two-layeredstructure, but the rigidity of the substrate may be enhanced byproviding third and fourth layers to close opening at a side opposite gothe vibrating section of the cavity. Alternatively, the ceramicsubstrate 1 may be formed by simultaneously laminating a layer to beused as a rear wiring board.

[0057] In this case, it may be that a thick film of a pattern providedwith a hollow space corresponding to a cavity may be printed as a secondlayer on a green sheet as a third layer by a thick film-forming method,such as a screen printing method, and a substrate having a three-layeredstructure is formed by laminating a green sheet for a first layercorresponding to a vibrating plate with the second layer, thermalcompression bonding and firing them.

[0058] The piezoelectric/electrostrictive operating section 5 is formedon the ceramic substrate 1 by the thick film-forming; method such as byscreen printing, spraying, dipping or coating or by a thin film-formingmethod such as ion beam, sputtering, vacuum deposition, ion plating, CVDor plating.

[0059] First, after a first electrode film (lower electrode) 2 is formedon a surface of a ceramic substrate 1 by the above film-forming method,a piezoelectric/electrostrictive layer 3 is similarly formed thereover.

[0060] The thick-film forming methods such as screen printing, dipping,coating and electrophoresis are advantageously suitable for theformation of the piezoelectric/electrostrictive layer 3.

[0061] The above methods are simple methods in the formation ofpiezoelectric films with use of a paste, a slurry, a suspension, anemulsion, a sol or the like composed mainly of piezoelectric ceramicparticles having the average grain size of 0.01 to 5.0 μm, preferably0.05 to 3.0 μm, and such methods afford good piezoelectric operatingcharacteristics. Further, the electrophoresis can not only form the filmat a high density with a high configuration precision, but also hasfeatures as described in a technical literature. Kazuo Anzai “DENKIKAGAKU 53”, No. 1 (1985) pp 63-68.

[0062] Therefore, the above-mentioned methods may be selectivelyappropriately used tinder consideration of the required precision andreliability.

[0063] Further, a desired shape of the abovepiezoelectric/electrostrictive layer 3 is realized by forming a patternthrough screen printing, photolithography or the like or by forming apattern through removal of an unnecessary portion via laser working witheximer or YAG, or machining such as slicing or ultrasonic machining.

[0064] The structure of the element produced there and the configurationof the filmy piezoelectric/electrostrictive operating section are neverrestrictive. Depending upon uses, any shape or configuration may beemployed for example, polygonal shapes such is triangle and rectangularshapes, round, shapes such as circular, elliptical and toroidal shapes,comb-like shape, lattice-like shape or peculiar shapes formed bycombining them in any manner may suffice.

[0065] The thus formed piezoelectric/electrostrictive layer 3 is fired(heat treatment) so that it may be integrated with the ceramic substrate1 via the lower electrode 2. In the present invention, this firing stepis particularly important.

[0066] That is, it is one of the objects of the present invention topropose. The piezoelectric/electrostrictive film type element whichcontrols both the evaporation of the lead element from thepiezoelectric/electrostrictive layer and the invasion of the leadelement into the substrate by adjusting the concentration of the lead inthe atmosphere during firing the piezoelectric/electrostrictive layer inthe presence of the vapor containing at least lead element generatedfrom the piezoelectric/electrostrictive material containing the leadelement as its constituent element or in the presence of an evaporatingsource of a lead-containing material for controlling the composition ofthe piezoelectric/electrostrictive layer. The rate of a heterophaseoccurring at the surface of the piezoelectric/electrostrictive layerafter the firing is used as an index for the judgment of the evaporatedamount of the lead element from the piezoelectric/electrostrictivelayer.

[0067]FIG. 3 shows results obtained by investigating the relationshipsbetween the heterophase-occurrence rate at the surface and thepiezoelectric/electrostrictive performance or the durability withrespect to piezoelectric/electrostrictive layers fired in variousconditions.

[0068] The piezoelectric/electrostrictive performance was evaluated by adisplacement performance, and the durability was evaluated by afrequency of cracking in the vibrating sections of the substrates.

[0069] As shown in FIG. 3, when excellent piezoelectric/electrostrictiveperformance and excellent durability were both obtained, theheterophase-occurrence rate was in a range of 0.1 to 30% in terms anarea rate. When this rate was 1 to 10%, particularly excellent resultswere obtained.

[0070] In order to produce the heterophase in an appropriate range onthe surface of the piezoelectric/electrostrictive layer after the filmformation as mentioned above, the concentration of lead in the firingatmosphere and/or the amount and the speed of the running fluid of thefiring atmosphere needs to he accurately adjusted.

[0071] Concrete controlling measures are as follows:

[0072] When a firing vessel is used in the concentration of lead in thefiring atmosphere and/or the amount and the speed of the running fluidof the firing atmosphere can be adjusted by controlling the packedamount of fired body (piezoelectric/electrostrictive material) and theopen degree of the firing vessel.

[0073] When the atmosphere is controlled with the evaporating source,the concentration of lead in the lead-containing firing atmosphereand/or the amount and the speed of the running fluid of the firingatmosphere in the vicinity of the fired body can be adjusted byadjusting the compositional ratio of the evaporating source containinglead as its constituting element, the configuration (molded bodies ofpowder or pellets employed, for example), weight, the arranged positionbetween the fired bodies and evaporating source, etc. In this case, thefiring atmosphere is more preferably adjusted by using the above firingvessel and placing the evaporating source therein).

[0074] Any evaporating source may be employed so long as it generates avapor containing at least lead element. Piezoelectric/electrostrictivematerials and their combinations mentioned later are preferred. Thepiezoelectric electrostrictive material having to same composition asthat of the piezoelectric/electrostrictive layer used is more preferablyused.

[0075] When the piezoelectric/electrostrictive material having the samecomposition as that of the piezoelectric/electrostrictive layer is usedas the evaporating source, a dummy pattern of which arrangement andconfiguration are adjusted may be formed on the ceramic substrate as anevaporating source, followed by firing. Alternatively, this dummypattern may be formed simultaneously with the formation of thepiezoelectric/electrostrictive layer, followed by firing.

[0076] In this case, the dummy pattern will be an effective measure foradjusting the concentration distribution of the firing atmosphere nearThe piezoelectric/electrostrictive layer formed on the same ceramicsubstrate

[0077] Control based on the arrangement of the substrate on firing thepiezoelectric/electrostrictive layer is performed as follows.

[0078] When plural sets of ceramic substrates formed withpiezoelectric/electrostrictive layers thereon are simultaneouslyintegrally fired, the arrangement of the ceramic substrates ispreferably adjusted under consideration of the vapors containing thelead element generated from the individual piezoelectric/electrostaticlayers.

[0079] When the ceramic substrates are fired in a staked state with useof setters (substrate-placing plates), the atmosphere near thepiezoelectric/electrostrictive layer is preferably adjusted underconsideration of the distance from the surface of thepiezoelectric/electrostrictive layer to the setter.

[0080] The above is applicable to cases where a firing vessel is used.In such cases, it is also preferable to adjust the firing atmospherenear the piezoelectric/electrostrictive layer under consideration of thedistance between the inner wall of the firing vessel.

[0081] Control with absorbing body is formed as follows. In order tomake inner the concentration of the vapor containing the lead element inthe firing atmosphere, the vapor concentration may be adjusted byarranging, around fired bodies, an absorbing body for absorbing the leadelement-containing vapor.

[0082] As to materials for absorbing the lead element-absorbing vapor,those capable of withstanding the firing temperature and readily toreact with the lead element, for example, titania, magnesia ad mulliteare preferably used.

[0083] The firing (thermally treating) temperature at which thepiezoelectric/electrostrictive layer is integrally formed on the ceramicsubstrate depends upon the material constituting them, and appropriatelydetermined under consideration of controlling of the atmosphere. Thetemperature is ordinarily 900 to 400° C., preferably 1000 to 1400° C.

[0084] It is considered that the heterophase occurring in the abovefiring treatment is formed through evaporation of a material having arelatively high vapor pressure, such as a lead-containing material, inthe composition constituting the piezoelectric/electrostrictivematerial.

[0085] The rate of the heterophase can be easily detected throughobservation of the piezoelectric/electrostrictive layer with an electronmicroscope or the like after the firing and monitoring of thedistribution of the components.

[0086] Since an emitted rate of reflected electrons forming a reflectedelectron image uniformly increase with increase in the atomic number,the reflective electron images obtained with the scanning electronmicroscope can generally be understood as difference in compositionthrough judging the magnitude of the atomic number based on the contrastof the image (A heavier element material can be observed more brightlythan a lighter element material). Observation of the surface propertieswith secondary electron images can be an effective measure for judgingdifferences in composition in more detail.

[0087] Therefore, since the reflective electron images of theheterophase portion occurring at the surface of thepiezoelectric/electrostrictive layer by firing represents a compositionlacking the lead element as a heavy element, the image is relativelydark. Accordingly, this image can be easily judged as the heterophaseportion.

[0088] Thereafter, a second electrode film 4 is formed on thepiezoelectric/electrostrictive layer 3 formed above and then fired as inthe same way as in the case of the first electrode film, therebycompleting the piezoelectric/electrostrictive operating section 5.

[0089] In the above, description is made of a case where the firstelectrode is formed and fired, the piezoelectric/electrostrictive layeris formed and fired, and finally the second electrode is formed andfired for the integration thereof. The formation (firing) of thepiezoelectric/electrostrictive operating section is not this method. Forexample the first electrode, the piezoelectric/electrostrictive layerand the second electrode may be successively formed and firedaltogether. Alternatively, it may be that the first electrode and thepiezoelectric/electrostrictive layer are successively formed andsimultaneously fired, and then the second electrode is formed and fired.Alternatively, the first electrode is formed and fired thepiezoelectric/electrostrictive layer and the second electrode layer arcsuccessively formed and simultaneously fired.

[0090] Among them, the successive formation and firing or the respectivelayers is more preferable, because the layers can be successively firedat their respective lower temperatures.

[0091] Next, preferred materials in each layer constituting thepiezoelectric/electrostrictive operating section will be explained.

[0092] The material for the first electrode film is not particularlylimited, so long as it can withstand an oxidizing atmosphere at aroundthe above-mentioned firing temperature. For example, metals alone oralloys, mixtures of such metals and alloys with insulating ceramics, andfurther conductive ceramics may be used. Among them, noble metals havinghigh melting points, such as platinum, palladium and rhodium, andelectrode materials composed mainly of alloys of silver-palladium,silver-platinum, or platinum-palladium are preferred. In particular,materials composed mainly of platinum are highly suitable.

[0093] It is preferred that the above-mentioned metals or alloys areadded with metal oxides, such as alumina, titania, zirconia, ceria,copper oxide, etc. It is also preferred that the material for the firstelectrode film is comprised of a cermet material wherein the sameceramic materials as those for the ceramic substrate orpiezoelectric/electrostrictive material, to be described hereinafter,are dispersed in the metal or alloy. When a cermet material is used asthe electrode, it is possible to achieve a significant functionaladvantage that deterioration with time of the displacing operation ofthe piezoelectric/electrostrictive element can be effectivelysuppressed.

[0094] When glass such as silicon oxide is used as an additive to thefirst electrode, it is likely to react with thepiezoelectric/electrostrictive layer during the heat treatment, whichcauses deterioration of the characteristics of the element. Therefore,use of such glass is preferably avoided. It is preferred that theaddition amount of the additive to the electrode is around 5 to 30 vol %in the case of the substrate material, and around 5 to 20 vol % <in thecase of the piezoelectric/electrostrictive material.

[0095] The second electrode film is not particularly limited to anymaterial. In addition to the materials to be used for the firstelectrode, sputtering films such as of gold, chronium and copper, orresinate (orgamometallic compound) print films comprised of gold orsilver may be used.

[0096] As the piezoelectric/electrostrictive material for thepiezoelectric/electrostrictive layer, any material may be used so longas it contains lead as its constituting element and exhibits electricfield-induced strain such as piezoelectric or electrostrictive effects.For example, the material may be crystalline or amorphous, or adielectric ceramic material, ferrodielectric ceramic material oranti-ferrodielectric ceramic material may be use. Further, the materialmay need a polarization treatment or no polarization treatment.

[0097] The piezoelectric/electrostrictive material constituting thepiezoelectric/electrostrictive layer may be adjusted to have a desiredcomposition and further a desired rate of the heterophase at the surfaceof the piezoelectric/electrostrictive layer by preliminary appropriatelyadjusting the compositional proportion of the lead element and alsoadjusting the composition with the firing atmosphere for integrallyfiring the piezoelectric/electrostrictive layer.

[0098] As preferred piezoelectric/electrostrictive materials, materialscomposed mainly of lead zirconate, titanate (PZT-based materials),materials composed mainly of lead titanate, materials composed mainly oflead zirconate, materials composed mainly of lead magnesium niobate(PMN-based materials), materials composed mainly of lead nickel niobate(PNN-based materials), materials composed mainly of lead magnesiumtungstonate, materials composed mainly of lead manganese niobate,material composed mainly of lead antimony stannate, materials composedmainly of lead zinc niobate, materials composed mainly of lead magnesiumtantalate, material composed mainly of lead nickel tantalate, andcomposite materials thereof may be recited.

[0099] To the above-mentioned materials may be incorporated asadditive(s) oxides and other compounds of lanthanum, barium, niobium,zinc, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium,tantalum, tungsten, nickel, manganese, lithium, strontium, magnesium,calcium, hitmus, stanum, etc. For example, PLZT-based materials inwhichanoxide or the like of landranum is added to a material composed mainlyof a PZT-based material may be used.

[0100] Addition of glass such as silicon oxide is preferably avoided,because it readily reacts with the piezoelectric/electrostrictivematerial and makes the maintenance of the desired material compositiondifficult.

[0101] Among the above piezoelectric/electrostrictive materials,materials composed mainly of lead magnesium niobates, lead zirconate andlead titanate, materials composed mainly of lead nickel niobate, leadmagnesium niobate, lead zirconate and lead titanate, materials composedmainly of lead nickel tantalate, lead magnesium niobate, lead zirconateand lead titanate, or materials composed mainly of lead magnesiumtantalite, lead magnesium niobate, lead zirconate and lead titanate arepreferably used.

[0102] Among them, the materials composed mainly of lead magnesiumniobates, lead zirconate and lead titanate are preferably used. For,such a material, not only has a high piezoelectric constant, but also itundergoes particularly less reaction with the substrate material duringthe heat treatment.

[0103] In the case of the multi-component basedpiezoelectric/electrostrictive material thepiezoelectric/electrostrictive characteristic changes depending upon thecomposition of the components. However, the three-component basedmaterial of lead magnesium niobate-lead zirconate-lead titanatefavorably used in the piezoelectric/electrostrictive element accordingto the present invention preferably has a composition near themorphotropic phase boundary of the pseudo-cubic crystal-tetragonalcrystal-rhombohedral crystal. Particularly, a composition composed of 15to 50 mol % of lead magnesium niobate, 10 to 45 mol % of lead zirconateand 30 to 45 mol % of lead titanate is advantageously used, because ithas a high piezoelectric constant and an electro mechanical couplingfactor.

[0104] As the material for constituting the ceramic substrate, ceramicmaterials composed mainly of zirconium oxide are advantageously suitablein acquiring properties that mechanical strength is high, theabove-mentioned beat treatment is possible around 1400° C., thepiezoelectric/electrostrictive operating section can be integrallylaminated without using an adhesive or the like, and operationalcharacteristics of large displacement and generated forces and highresponse speed are excellent. Particularly, the materials composedmainly of zirconium oxide completely or partially stabilized with atleast one of yttrium oxide, ytterbium oxide, cerium oxide, calcium oxideand magnesium oxide is preferred. Namely, such a material makes itpossible to obtain a high mechanical strength and a high toughness evenwhen the substrate has a small thickness. Further, such a materialundergoes a small stress upon a heat treatment together with apiezoelectric/electrostrictive material adopted in the film-formingmethod. Moreover, such a material exhibits less chemical reactivity withthe piezoelectric/electrostrictive material.

[0105] The addition amount of the above mentioned compound forstabilizing zirconium oxide is preferably 1 to 30 mol % for yttriumoxide or ytterbium oxide, 6 to 40 mol % of cerium oxide and around 5 to40 mol % of calcium oxide or magnesium oxide. Among them, yttrium oxideis particularly preferably used as the stabilizer. In this case, it ispreferably not less than 2 mol % from the standpoint of assuringexcellent durability even in a case where lead enters the substrate onfiring the piezoelectric/electrostrictive layer and not more than 8 mol% form the standpoint of obtaining structurally excellent strength. thecrystalline phase of zirconium oxide added with yttrium oxide ispartially stabilized in such an addition range, which enables theproduction of the substrate having excellent substrate characteristics.

[0106] Further the concentration of the lead containing atmosphere forintegrally firing the piezoelectric/electrostrictive layer isappropriately adjusted, more concretely when the occurring rate of theheterophase at the surface of the piezoelectric/electrostrictive layersatisfies a range of 0.1 to 30% in terms of the area percentage, thedurability of the piezoelectric/electrostrictive element can be furtherenhanced by increasing the addition amount of yttrium oxide in a rangeof 2 to 8 mol %.

[0107] On the other hand, if the occurrence rate of the heterophase atthe surface of the piezoelectric/electrostrictive layer is less 0.1% interms of the area percentage, sufficient durability cannot be obtainedeven by adjusting the addition amount of yttrium oxide in the range of 2to 8 mol %.

[0108] Furthermore, sintering aid(s) such as aluminum oxide or titaniumoxide or further clay may be added to such stabilized zirconium. In thiscase, it is preferable to adjust the composition and the addition amountof the sintering aid so that 1% or more of silicon oxide. (SiO₂, SiO)may not he included in the fired substrate. Because if excessive siliconoxide is included in the substrate, the substrate is likely to undergo areaction will the piezoelectric material during heat treatment, whichmakes controlling of the composition difficult.

[0109] Next, preferable thicknesses of each of the ceramic substrate andeach of the layers constituting the piezoelectric/electrostrictiveoperating section will be explained.

[0110] Ceramic Substrate

[0111] At least a part of that portion of the ceramic substrate in thisembodiment which the piezoelectric/electrostrictive operating section isformed is preferably designed as a thin portion. The thicknesses of thesubstrate is generally not more than 50 μm, preferably not more than 30μm, more preferably not more than 15 μm so as to obtain high responseand large displacements of the filmy element.

[0112] Further, particularly in the thin portion, the average grain sizeof crystals is generally preferably 0.1 to 2.0 μm, and more preferablynot less than 0.1 μm and not more than 1.0 μm so as to improve theoperating characteristics of the piezoelectric/electrostrictiveoperating section formed on such thin portion, thereby giving largedisplacements and large forces as an actuator or a detecting portion,for example.

[0113] In addition, in a unitary planar ceramic substrate as shown inFIG. 1(a), in order to achieve a high speed response characteristic anda large displacement of the film-type element, the thickness of theceramic substrate is generally not more than 50 mm, preferably not morethan 30 μm, and more preferably not more than 15 μm.

[0114] Furthermore, in at least that portion of the ceramic substrate inwhich the piezoelectric/electrostrictive operating section is formed,the average grain size of crystals is generally preferably 0.1 to 2.0μm, more preferably not more than 1.0 μm so as to enhance the operatingcharacteristic of the piezoelectric/electrostrictive operating sectionand to give large displacements and large forces as an actuator or adetecting portion, for example.

[0115] Electrode Film

[0116] The thickness of the electrode film formed using the aboveconductive material is generally not more than 20 μm, preferably notmore than 5 μm. Particularly the upper electrode formed has a thicknesspreferably not more than 1 μm, more preferably 0.5 μm.

[0117] Piezoelectric/electrostrictive Layer

[0118] The thickness of the piezoelectric/electrostrictive layer formedusing the above piezoelectric/electrostrictive layer is generally notmore than 100 μm preferably not more than around 50 μm and morepreferably not more than around 3 μm to 40 μm so as to give largedisplacements at a relatively low operating voltage.

[0119] The thickness of the entire piezoelectric/electrostrictiveoperating section constituted by the abovepiezoelectric/electrostrictive, layer, the lower electrode and the upperelectrode is generally not more than 150 μm, preferably 50 μm.

[0120] In the above, explanation has been made with respect to thepiezoelectric/electrostrictive film type element as shown in FIGS. 1(a)and 1(b). as a typical example, though the present invention is notlimited to this embodiment. The invention is also applicable topiezoelectric/electrostrictive film type elements having the structuresexplained below.

[0121] That is, an element shown in FIG. 4 is a bimorph type of apiezoelectric/electrostrictive film type element in whichpiezoelectric/electrostrictive operating sections 5 are provided at eachof front and rear surfaces of a thin portion of a ceramic substrate 1.

[0122] In case of embodiments in FIGS. 5 to 8, a plurality ofpiezoelectric/electrostrictive operating sections 5 are provided on aceramic substrate in parallel. Particularly in the elements shown inFIGS. 5 and 6, slits 7 are formed at the ceramic substrate 1 locatedbetween these plural piezoelectric/electrostrictive operating sections5, so that the piezoelectric/electrostrictive operating sections 5 areindependent. In the element of FIG. 7, slender rectangular holes 8 eachhaving a slender shape are provided in the ceramic substrate 1 at apredetermined pitch to give a ladder-like shape of die ceramic substrate1. A piezoelectric/electrostrictive operating section 5 is formed ateach of connecting portions 2 a of the ladder-shaped ceramic substrate 1sandwiched between the adjacent rectangular holes 8, 8.

[0123] In FIGS. 5, 9 denotes a back portion to thepiezoelectric/electrostrictive layer 3, which is an insulating film forelectrically insulating the first electrode film 2 form the secondelectrode film 4.

[0124] In the element of FIG. 8, a plurality ofpiezoelectric/electrostrictive operating sections 5 are integrallyprovided on a unitary large ceramic substrate 1 at a predetermined pitch

[0125] FIGS. 9(a) and 9(b) show an embodiment in which the configurationof the ceramic substrate and the arrangement of thepiezoelectric/electrostrictive, operating sections 5 arm modified fromthose in the element shown in FIG. 8.

[0126] That is, as clear from the configuration of a rear face of thesubstrate shown in FIG. 9(a), cavities 6 each having a predeterminedsize are provided in the rear face of the thick ceramic substrate 1 at apredetermined pitch in a zigzag fashion, so that the substrate has astructure in which vibrating sections 1 a provided by bottoms of thecavities 6 are arranged zigzag. A shown in FIG. 9(b), thepiezoelectric/electrostrictive operating sections 5 are integrallyformed and arranged zigzag on the substrate, while located on thevibrating sections 1 a, respectively.

[0127] In each of the thus constructed elements, the voltage is appliedacross two electrode constituting the piezoelectric/electrostrictiveoperating section in the same manner as conventionally so that theelement may function as an actuator. Thereby, the electric field actsupon the piezoelectric/electrostrictive layer, which causes an electricfield-induced strain in the piezoelectric/electrostrictive. layer basedon the this electric field. Consequently, a bending displacement or aforce is generated in a direction vertical to the planar surface of theceramic substrate.

[0128] In the present invention no particular limitation is posed on theconnecting way for each electrode. Any of formerly known connecting waysshown in FIGS. 10 to 12 may be employed.

[0129] FIGS. 10(a) and 10(b) shows wires connected to lower electrodes 2through through-holes 10 (illustration to an upper electrode patternomitted), and FIG. 11 is a modification of the embodiment of FIGS. 10(a)and 10(b). FIG. 12 shows wires connected to upper electrodes 4 throughthough-holes 10 (illustration of a lower electrode pattern omitted).

[0130] In FIG. 10(b), reference numeral 11 denotes a window portion, 12a spacer layer, 13 a thin planar layer forming vibrating sections, and14 a base layer functioning as a reinforcing substrate portion and awiring substrating portion. Opening holes are formed in the base layer14.

[0131] FIGS. 13(a) and 13(b) show an embodiment of apiezoelectric/electrostrictive film type actuator in which a pluralityof pressurizing chambers are provided in parallel in a row, andpiezoelectric/electrostrictive operating sections are providedcorresponding to the respective pressurizing chambers. FIGS. 13(a) and13(b) are a decomposed view and a sectional view of the embodiment.

[0132] In this embodiment, a spacer layer 12 in which plural windows 11are provided in parallel in a row, a thin planar layer 13 forming avibrating section, and a base layer 14 are laminated one upon another,and integrally fired, so that the piezoelectric/electrostrictiveoperating sections 5 are integrally formed with the ceramic substrate 15having the pressurizing chambers formed with the windows 11, whilelocated corresponding to the respective pressurizing chambers at theouter surface of the thin planar layer 13.

[0133] FIGS. 14(a) and 14(b) show an acceleration sensor which isconstituted by a weight 16, support bases 17, and a flexible plate 22has piezoelectric elements 21 a and 21 b where a piezoelectric body 18is held between a set of electrodes 19 a, 19 b and 20, so that electriccharges is generated form the piezoelectric body 18 depending uponbending of the flexible plate 22 corresponding to an accelerationapplied from the outside, and the direction and the magnitude of theacceleration is three-dimensionally detected based such electriccharges.

[0134] In this embodiment, the piezoelectric elements 21 arecontinuously arranged on top portions of the weight 16 and/or thesupport bases 17 in flexing portions 22 a of the flexible plate 22.

[0135] This acceleration sensor element is produced by laminatingintermittent-layered green sheets of the weight 16, the support bases 17and the flexible plate 22, forming a laminate by compression bonding,obtaining a fired body by integrally firing the laminate, forming thepiezoelectric elements 21 a and 21 b by a thick film-forming method andfiring the resultant.

[0136]FIG. 15 shows a piezoelectric/electrostrictive film typedisplacement element to which the present invention applied. In thisfigure, 23 is a movable portion, 24 a stationary portion and 25 aterminal electrode.

[0137] Next, uses of the integrated piezoelectric/electrostrictive filmtype elements obtained according to the present invention will beexplained.

[0138] The piezoelectric/electrostrictive elements according to thepresent invention can be advantageously used as unimorph type elementsor bimorph type elements for various transducers which convert theelectric energy to the mechanical energy, that is, mechanicaldisplacements, forces or vibrations, as well as elements for effectingreverse conversion thereof, various actuators, functional partsoperating at a predetermined frequency range such as filters, variousdisplay devices such as displays, transformers, sound-emitting devicessuch as microphones and loudspeakers, communication and power vibrators,resonators and transmitters, magnetic head-locating elements such ashard discs, optical shutters, discriminators, various sensors such asultrasonic sensors, accelerator sensors, angular velocity sensors,impact sensors, mass sensors and gyroscopes, and also for servodisplacement elements, pulse driven motors, ultrasonic motors,piezoelectric fans, piezoelectric relays, etc., as described in KenjiUchino, “PIEZOELECTRIC/ELECTROSTRICTIVE ACTUATORS: FUNDAMENTAL TOAPPLIED TECHNIQUES”, edited by Japan Industrial Technical Center. Thepiezoelectric/electrostrictive elements according to the presentinvention can also be advantageously adopted by various actuators,vibrators, sound-emitting devices, display devices, etc.

[0139] Since the piezoelectric/electrostrictive element according to thepresent invention has a dielectric property in addition to thepiezoelectric/electrostrictive characteristic, it may be used as a filmcondenser element.

EXAMPLE

[0140] A ceramic substrate was made of zirconium oxide added with 3 mol% of yttrium oxide. Green sheets for a vibrating plate (a substrate anda surface layer) and a green sheet for a support member provided withopening holes for the formation of a 1 mm×1 mm cavity were laminated,thermally compression bonded and fired at 1500° C., and then apiezoelectric/electrostrictive operating section was formed on thesubstrate by screen printing.

[0141] At that time, a first electrode film (lower electrode) and anupper electrode film (upper electrode) were made of platinum and goldrespectively, and fired at 1300° C. and 600° C., respectively. Thethicknesses of the electrode films were 3.0 μm and 0.5 μm, respectively.A piezoelectric/electrostrictive layer was made of a material composedmainly of lead zirconate, lead titanate and lead magnesium niobate.

[0142] The following combinations in thickness were selectively adoptedbetween the piezoelectric/electrostrictive layer and the vibratingportion of the ceramic substrate.

[0143] (1) Piezoelectric/electrostrictive layer 10 μm thick, vibratingportion of the substrate 6 μm

[0144] (2) Piezoelectric/electrostrictive layer 30 μm thick, vibratingportion of the substrate 15 μm

[0145] The above piezoelectric/electrostrictive layer was fired by usinga ceramic firing vessel of 150 mm×150 mm×100 mm which was spaced from alid covering the vessel by 0 to 0.5 mm to control an open degree of thefiring vessel. The same material as that of thepiezoelectric/electrostrictive material was put as an evaporating sourceinto the firing vessel in an charged amount of 0 to 50 g. The firingtemperature was 1250° C.

[0146] Tables 1 and 2 give the relationship betweenheterophase-occurrence rate and the durability at the surface of thepiezoelectric/electrostrictive layer after firing examined, and Tables 3and 4 also give the relationship between heterophase-occurrence rate andthe insulating characteristic examined.

[0147] Durability was judged based on the changed percentage relative tothe initial displacement and the warped amount for the substrate havinga square shape of 40 mm×40 mm when the product was used at a temperatureof 95° C. in an atmosphere with a humidity of 95% for 100 to 500 hours,and evaluated by the following standard.

[0148] Characteristic (Changed percentage relative to initialdisplacement)

[0149] ⊚: less than 10%

[0150] ◯: not less than 10%, less than 15%

[0151] Δ: not less than 15%, less than 30%

[0152] x: not less than 30%

[0153] Warping (Warped amount to the 40 oxide mm×40 mm substrate)

[0154] ⊚: less than 15 μm

[0155] ◯: not less than 15%, less than 30 μm

[0156] Λ: not less 30 μm, less than 50 μm

[0157] x: not less than 50 μm.

[0158] Insulating characteristic

[0159] The insulating characteristic was judged based on the number ofelements in which dielectric breakdown occurred when 2 kV/mm and 5 kV/mmvoltages were applied, and evaluated by the following standard.

[0160]

: 0 elements/1000 elements

[0161] ◯: 1-10 elements/1000 elements

[0162] Δ: 11-100 elements/1000 elements TABLE 1 Thickness ofpiezoelectric/electrostrictive layer: 10 μm Thickness of vibratingportion of substrate: 6 μm Heterophase occurrence Durability 100 hDurability 300 h Durability 500 h No. rate (%) characteristic warpingcharacteristic warping characteristic warping 1 0 Δ Δ x x fracturedfrac- tured 2 0.1 ∘ ∘ ∘ ∘ ∘ ∘ 3 0.5 ⊚ ⊚ ⊚ ⊚ ∘ ∘ 4 1 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 5 5 ⊚ ⊚⊚ ⊚ ⊚ ⊚ 6 10 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 7 20 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 8 30 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 9 35 ⊚ ⊚ ⊚ ⊚⊚ ⊚

[0163] TABLE 2 Thickness of piezoelectric/electrostrictive layer: 30 μmThickness of vibrating portion of substrate: 15 μm Heterophaseoccurrence Durability 100 h Durability 300 h Durability 500 h No. rate(%) characteristic Warping characteristic warping characteristic warping1 0 x x fractured frac- — — tured 2 0.1 ∘ ∘ ∘ ∘ ∘ ∘ 3 0.5 ⊚ ∘ ∘ ∘ ∘ ∘ 41 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 5 5 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 6 10 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 7 20 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 8 30 ⊚ ⊚⊚ ⊚ ⊚ ⊚ 9 35 ⊚ ⊚ ⊚ ⊚ ⊚ ⊚

[0164] TABLE 3 When 2 kV/mm applied Heterophase Thickness ofpiezoelectric/ occurrence rate electrostrictive layer No. (%) 10 μm 30μm 1 0 ⊚ ⊚ 2 0.1 ⊚ ⊚ 3 0.5 ⊚ ⊚ 4 1 ⊚ ⊚ 5 5 ⊚ ⊚ 6 10 ⊚ ⊚ 7 20 ◯ ◯ 8 30 ◯◯ 9 35 Δ ◯

[0165] TABLE 4 When 5 kV/mm applied Heterophase Thickness ofpiezoelectric/ occurrence rate electrostrictive layer No. (%) 10 μm 30μm 1 0 ⊚ ⊚ 2 0.1 ⊚ ⊚ 3 0.5 ⊚ ⊚ 4 1 ⊚ ⊚ 5 5 ⊚ ⊚ 6 10 ⊚ ⊚ 7 20 ◯ ◯ 8 30 ◯◯ 9 35 Δ Δ

[0166] As shown in Tables 1 and 2, there is a strong relationshipbetween the heterophase-occurrence rate at the surface of thepiezoelectric/electrostrictive layer and the durability. When theheterophase-occurrence rate is not less than 0.1%, excellent durabilityis obtained. Particularly, when the heterophase-occurrence rate is notless than 1%, extremely excellent durability is obtained.

[0167] As shown in Tables 3 and 4, there is also a strong relationshipbetween the heterophase-occurrence rate at the surface of thepiezoelectric/electrostrictive layer and the insulating characteristic.When the heterophase-occurrence rate is not more than 30%, excellentinsulation characteristic is obtained. Particularly, when theheterophase-occurrence rate is not more than 10%, extremely excellentinsulation characteristic is obtained.

[0168] Since firing is conventionally effected under such condition tolayer on firing, the heterophase-occurrence rate is almost zero afterthe firing. Accordingly, no problem occurred in thepiezoelectric/electrostrictive characteristic and the insulationcharacteristic, but durability was inevitably conspicuouslydeteriorated.

[0169] FIG 16 shows a reflective electron image in the observation of asurface of the piezoelectric/electrostrictive layer after the filingwith a scanning electron microscope. As seen from FIG. 16, theheterophase portion has a relatively dark image, and can be easilydiscriminated. The heterophase-occurrence rate in tis case was 5%.

[0170] As mentioned above, the present invention enables the stableproduction of the piezoelectric/electrostrictive element which exhibitsexcellent durability and excellent piezoelectric/electrostrictivecharacteristic, even when the integrated piezoelectric/electrostrictivefilm type element is used in a high-temperature and highly humidatmosphere.

1. An integrated piezoelectric/electrostrictive film type element havingexcellent durability and comprising a substrate made of a ceramicmaterial composed mainly of completely stabilized or partiallystabilized zirconium oxide, and a piezoelectric/electrostrictiveoperating section integrated onto the ceramic substrate by afilm-forming method, said piezoelectric/electrostrictive operatingsection comprising a lower electrode, a piezoelectric/electrostrictivelayer of a lead element-containing composition, and an upper electrode,wherein a heterophase-occurrence rate at a surface of thepiezoelectric/electrostrictive layer is controlled to a range of 0.1 to30%.
 2. The integrated piezoelectric/electrostrictive film type elementaccording to claim 1, wherein the ceramic substrate is shaped in theform of a thin diaphragm portion, a said piezoelectric/electrostrictiveoperating section is integrally formed on an outer surface of thediaphragm portion.
 3. The integrated piezoelectric/electrostrictive filmtype element according to claim 1 or 2, wherein theheterophase-occurrence rate is controlled to a range of 1 to 10%.
 4. Theintegrated piezoelectric/electrostrictive film type element according toclaim 1 or 2, wherein the average grain size, of crystals constitutingthe ceramic substrate is 0.1 to 2.0 μm.
 5. The integratedpiezoelectric/electrostrictive film type element according to claim 1 or2, wherein a thickness of the piezoelectric/electrostrictive layer isnot more than 100 μm.
 6. The integrated piezoelectric/electrostrictivefilm type element according to claim 1 or 2, wherein a thickness of thepiezoelectric/electrostrictive operating section is not more than 150μm.
 7. The integrated piezoelectric/electrostrictive film type elementaccording to claim 2, wherein a thickness of the diaphragm portion isnot more than 50 μm.
 8. A process for producing an integratedpiezoelectric/electrostrictive film type element having excellentdurability, comprising the steps of preparing a substrate made of aceramic material composed mainly of completely stabilized or partiallystabilized zirconium oxide, and successively forming a lower electrode,a piezoelectric/electrostrictive layer of a lead element-containingcomposition, and an upper electrode on the ceramic substrate by afilm-forming period, said lower electrode, saidpiezoelectric/electrostrictive layer and the upper electrodeconstituting a piezoelectric/electrostrictive operating section and atleast said piezoelectric/electrostrictive layer being fired, wherein aproduced rate of a heterophase occurring at a surface of thepiezoelectric/electrostrictive layer is controlled Lo a range of 0.1 to30% in terms of an area rate by adjusting a concentration of lead in afiring atmosphere and/or an amount and a speed of a running fluid of thefiring atmosphere.
 9. The integrated piezoelectric/electrostrictive filmtype element-producing process according to claim 8, wherein theatmosphere is controlled by adjusting at least one condition selectedfrom: i) a composition ratio, a configuration, a weight and an arrangedlocation of an evaporating source containing lead as a constituentelement; ii) an arranged locations of a piezoelectric/electrostrictivematerial in a firing furnace or a firing vessel iii) an opening degreeof the firing furnace or the firing vessel; and iv) feeding an absorbentfor absorbing a lead element in the firing atmosphere.